In several experiments, masked repetition priming in the lexical decision task was greater when prime validity, defined as the proportion of repetition versus unrelated primes, was high (.8 vs. .2), even though primes were displayed for only 45 or 60 ms. A similar effect was also found with masked semantic primes. Prime validity effects are not predicted on a lexical entry-opening account of masked priming nor are they consistent with the use of prime validity effects as a marker for the consciously controlled use of primes. Instead, it is argued that episodic traces are formed even for masked primes, are available as a resource that can aid word identification, and are generally more likely to be recruited when their validity is high. However, prime validity effects did not obtain when targets varied markedly from trial to trial in how easy they were to process. Here, it appears that trial-to-trial discrepancies made the lexical decision task more difficult, causing an increase in prime recruitment, at least when prime validity was low. Consistent with this claim, prime validity effects emerged when these trial-to-trial discrepancies were minimized.